One-shot Ubuntu agent2 installer (active checks)

README.md

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+# zabbix-agent
+
+One-shot [Zabbix agent2](https://www.zabbix.com/) installer for Ubuntu,
+using **active checks** — the agent connects *out* to the server, so it
+works behind NAT/firewalls and needs no inbound ports.
+
+- Idempotent — safe to re-run
+- Installs from the official Zabbix apt repo (agent2)
+- Config: `ServerActive=<server>`, `Server=127.0.0.1,<server>`,
+  `Hostname=<name>` (defaults to the short system hostname)
+
+## Use
+
+```bash
+# clone once, then git pull for updates:
+git clone https://gitea.noctools.nz/noctools/zabbix-agent.git
+sudo ./install-zabbix-agent2-ubuntu.sh --server <server-ip-or-name>
+```
+
+Or with no local copy at all:
+
+```bash
+curl -fsSL https://gitea.noctools.nz/noctools/zabbix-agent/raw/branch/main/install-zabbix-agent2-ubuntu.sh \
+  | sudo bash -s -- --server <server-ip-or-name>
+```
+
+## Flags
+
+| flag | meaning | default |
+|---|---|---|
+| `--server HOST[:PORT]` | Zabbix server/proxy for active checks (**required**) | — |
+| `--hostname NAME` | Zabbix host name — must equal the technical name on the server | short system hostname |
+| `--major X.Y` | Zabbix repo series | `7.4` |
+
+After installing, create the host on the Zabbix server with the **exact same
+technical name** and an active-agent template (e.g. "Linux by Zabbix agent
+active"). The script reports whether the agent reached the server and warns
+if the host doesn't exist yet — the warning clears by itself once it does.

install-zabbix-agent2-ubuntu.sh

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+#!/usr/bin/env bash
+# install-zabbix-agent2-ubuntu.sh — one-shot Zabbix agent2 (ACTIVE checks)
+# installer for Ubuntu. Public-safe: nothing about any specific environment
+# is baked in; the server address comes from the required --server flag.
+#
+# Idempotent — safe to re-run. What it does:
+#   1. Installs Zabbix agent2 from the official Zabbix apt repo
+#   2. Writes an ACTIVE-check config (agent connects OUT to the server;
+#      no inbound ports, no firewall changes needed — works behind NAT):
+#        ServerActive=<server from --server>
+#        Server=127.0.0.1,<server host>
+#        Hostname=<--hostname, else the short system hostname>
+#   3. Enables + restarts the service and sanity-checks the connection.
+#
+# Usage:
+#   sudo ./install-zabbix-agent2-ubuntu.sh --server 203.0.113.10
+#   sudo ./install-zabbix-agent2-ubuntu.sh --server 203.0.113.10:10051 --hostname web01
+#   sudo ./install-zabbix-agent2-ubuntu.sh web01 --server 203.0.113.10   # positional hostname
+#
+# One-liner (no local copy needed):
+#   curl -fsSL <repo-url>/install-zabbix-agent2-ubuntu.sh | sudo bash -s -- --server 203.0.113.10
+#
+# After it succeeds, the host must exist on the Zabbix server with the EXACT
+# same technical name (an active-agent template, e.g. "Linux by Zabbix agent
+# active"). The script warns if the agent cannot fetch its config yet — that
+# warning clears by itself within ~a minute of the host being created.
+
+set -euo pipefail
+
+ZABBIX_MAJOR="7.4"
+CONF="/etc/zabbix/zabbix_agent2.conf"
+LOG="/var/log/zabbix/zabbix_agent2.log"
+
+say() { echo "[zabbix-agent2] $*"; }
+die() { echo "[zabbix-agent2] ERROR: $*" >&2; exit 1; }
+usage() {
+    cat <<EOF
+usage: sudo $0 --server HOST[:PORT] [--hostname NAME] [--major X.Y]
+
+  --server HOST[:PORT]   required — Zabbix server/proxy for active checks
+                         (IP or DNS name; port defaults to 10051)
+  --hostname NAME        Zabbix host name (default: short system hostname;
+                         MUST equal the technical host name on the server)
+  --major X.Y            Zabbix major version from the official repo
+                         (default: ${ZABBIX_MAJOR}; use your server's version)
+  NAME (positional)      shorthand for --hostname NAME
+EOF
+}
+
+# ---- args --------------------------------------------------------------------
+SERVER_RAW=""
+HOSTNAME_ARG=""
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --server)        SERVER_RAW="${2:?}"; shift 2 ;;
+        -n|--hostname)   HOSTNAME_ARG="${2:?}"; shift 2 ;;
+        --major)         ZABBIX_MAJOR="${2:?}"; shift 2 ;;
+        -h|--help)       tail -n +2 "$0" | grep '^#' | sed 's/^# \{0,1\}//'; exit 0 ;;
+        *)               HOSTNAME_ARG="$1"; shift ;;
+    esac
+done
+
+[ -n "$SERVER_RAW" ] || { usage; die "--server is required"; }
+[[ "$ZABBIX_MAJOR" =~ ^[0-9]+\.[0-9]+$ ]] || die "--major must look like 7.4, not '${ZABBIX_MAJOR}'"
+
+# server HOST[:PORT] -> SA_HOST / SA_PORT (plain IPv4 or DNS name)
+case "$SERVER_RAW" in
+    *:*) SA_HOST="${SERVER_RAW%%:*}"; SA_PORT="${SERVER_RAW##*:}" ;;
+    *)   SA_HOST="$SERVER_RAW";       SA_PORT="10051" ;;
+esac
+[[ "$SA_PORT" =~ ^[0-9]+$ ]] || die "bad port in --server '${SERVER_RAW}' (IPv6 literals: give a DNS name instead)"
+[ -n "$SA_HOST" ] && [ "$SA_HOST" != "$SA_PORT" ] || die "bad --server '${SERVER_RAW}'"
+SA_ADDR="$SA_HOST"; [ "$SA_PORT" = "10051" ] || SA_ADDR="${SA_HOST}:${SA_PORT}"
+
+ZBX_HOSTNAME="${HOSTNAME_ARG:-$(hostname -s)}"
+case "$ZBX_HOSTNAME" in
+    *[!A-Za-z0-9._-]*) die "hostname '${ZBX_HOSTNAME}' has odd chars — pass --hostname <exact Zabbix technical name>" ;;
+esac
+
+[ "$(id -u)" -eq 0 ] || die "run as root (sudo)"
+
+# ---- platform ----------------------------------------------------------------
+. /etc/os-release
+[ "${ID:-}" = "ubuntu" ] || die "Ubuntu only (found '${ID:-unknown}'); for Debian, swap 'ubuntu' for 'debian' in the repo URL below"
+say "Ubuntu ${VERSION_ID} (${PRETTY_NAME:-ubuntu}) → server ${SA_ADDR}, hostname '${ZBX_HOSTNAME}'"
+
+# ---- 1. repo + package ---------------------------------------------------------
+export DEBIAN_FRONTEND=noninteractive
+APT_OPTS="-y -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold"
+
+apt-get update -qq
+apt-get install -qq $APT_OPTS ca-certificates curl >/dev/null
+
+DEB_URL="https://repo.zabbix.com/zabbix/${ZABBIX_MAJOR}/release/ubuntu/pool/main/z/zabbix-release/zabbix-release_latest_${ZABBIX_MAJOR}+ubuntu${VERSION_ID}_all.deb"
+curl -fsSI -o /dev/null "$DEB_URL" || die "no zabbix-release for Ubuntu ${VERSION_ID} (check --major); looked at ${DEB_URL}"
+curl -fsS -o /tmp/zabbix-release.deb "$DEB_URL"
+dpkg -i /tmp/zabbix-release.deb || apt-get -f install -qq $APT_OPTS
+rm -f /tmp/zabbix-release.deb
+apt-get update -qq
+apt-get install -qq $APT_OPTS zabbix-agent2
+say "installed: $(zabbix_agent2 -V | head -1)"
+
+# ---- 2. config (replace-or-append: one authoritative line per key) -------------
+if [ -f "$CONF" ] && [ ! -f "${CONF}.pre-install.bak" ]; then
+    cp -a "$CONF" "${CONF}.pre-install.bak"
+    say "backed up stock config to ${CONF}.pre-install.bak"
+fi
+
+set_conf() { # file key value — drop every existing (commented) line, append ours
+    sed -i -E "/^[[:space:]]*#?[[:space:]]*${2}=/d" "$1"
+    echo "${2}=${3}" >> "$1"
+}
+[ -f "$CONF" ] || die "expected ${CONF} to exist after install"
+
+set_conf "$CONF" ServerActive "$SA_ADDR"
+set_conf "$CONF" Server       "127.0.0.1,${SA_HOST}"
+set_conf "$CONF" Hostname     "$ZBX_HOSTNAME"
+
+# ---- 3. service + sanity -------------------------------------------------------
+systemctl enable zabbix-agent2 >/dev/null
+systemctl restart zabbix-agent2
+sleep 3
+systemctl is-active --quiet zabbix-agent2 || { journalctl -u zabbix-agent2 -n 20 --no-pager; die "service not active"; }
+zabbix_agent2 -t agent.version >/dev/null 2>&1 || die "agent fails to parse config / answer local test"
+
+# Active-check reachability: give the agent ~20s to fetch its first config.
+loggrep() { # pattern — agent log file, else the journal
+    if [ -r "$LOG" ]; then grep -Eqi "$1" "$LOG"; else journalctl -u zabbix-agent2 --since '-2 min' | grep -Eqi "$1"; fi
+}
+WARN=""
+for _ in $(seq 1 10); do
+    if loggrep 'started to fail|cannot obtain|no active checks|host not found'; then WARN=1; break; fi
+    sleep 2
+done
+
+echo
+say "done. config:"
+grep -E '^(Server|ServerActive|Hostname)=' "$CONF" | sed 's/^/    /'
+if [ -n "$WARN" ]; then
+    say "WARNING: agent cannot fetch its config yet:"
+    if [ -r "$LOG" ]; then tail -n 4 "$LOG" | sed 's/^/    /'
+    else journalctl -u zabbix-agent2 -n 4 --no-pager | sed 's/^/    /'; fi
+    say "expected if the host doesn't exist on the Zabbix server yet — create it"
+    say "with the EXACT technical name '${ZBX_HOSTNAME}' and an active-agent"
+    say "template; the warning clears by itself within a minute."
+else
+    say "active checks OK (no connection errors in the agent log)."
+fi